magnetohydrodynamics

[auberon36]

not magneto hydrodynamics, you just attract or repulse electro magnet with a magnet . Real electromagnetodynamics is Laplace Theorem, you create magnetic field perpendicular to a current you obtain a force perpendicular to both others... also named three fingers theorems . for your boat you need inside a magnet with vertical fields and outside on eachside electrodes with a battery giving horizontal current between each side of your boat, depending of sens of current your boat will go on or back

[johnroach1]

This is an open system, because the electrodes are going into the water under

the container.